It has been known that a crosslinked resin formed object is obtained by crosslinking, with a crosslinking agent such as an organic peroxide or the like, a cycloolefin resin obtained by ring-opening polymerizing a cycloolefin such as norbornene in the presence of a metathesis polymerization catalyst. It is known that the crosslinked resin formed object is excellent in electric characteristics such as a low dielectric constant and a low dielectric loss tangent in addition to a mechanical strength and a chemical resistance. Focusing on these characteristics, a film-shaped resin formed object has been manufactured, for example, by casting a solution obtained by dissolving a cycloolefin polymer and a crosslinking agent into a solvent onto a flat plate, and then evaporating the solvent by heat at the same time crosslinking. Further, a proposal that the film-shaped resin formed object obtained is laminated with a substrate for printed wiring board or the like to produce a crosslinked resin composite used for electronic parts has been suggested. In Japanese Patent Application Laid-Open No. 6-248164, disclosed are: a film obtained by casting a norbornene resin composition obtained by dissolving a thermoplastic hydrogenated ring-opening norbornene resin, an organic peroxide and a crosslinking agent into a solvent onto a supporting body and then drying; and a crosslinked resin composite obtained by pressing, heating and crosslinking the laminate of a copper foil and a prepreg obtained by impregnating a fiber reinforcement with the above norbornene resin composition and then drying. However, the crosslinked resin composite obtained by above method does not have a sufficient heat resistance enough to produce electronic parts by using a lead-free solder that has been adopted as an environmental protection. Further, there is a problem that the process is complicated because it is necessary to remove a solvent to obtain a film-shaped crosslinked resin formed object. To solve the problem, in Japanese Patent Application National Publication No. 11-507962, proposed is a method for obtaining a crosslinked resin by producing a cycloolefin polymer by ring-opening polymerizing a cycloolefin without a solvent in the presence of a ruthenium carbene complex and a peroxide, and then conducting post-curing (or post-crosslinking).